Fluid cushion confining system for ground effect machines



J. H. BERTIN Sept. 9, 1969 FLUID CUSHION CONFINING SYSTEM FOR GROUND EFFECT MACHINES Original Filed Jan. 11, 1962 2 Sheets-Sheet l J. H. BERTIN Sept. 9, 1969 FLUID CUSHION CONFINING SYSTEM FOR GROUND EFFECT MACHINES 2 Sheets-Sheet 2 Original Filed Jan. 11, 1962 United States Patent 3,465,845 FLUID CUSHION CONFINING SYSTEM FOR GROUND EFFECT MACHINES Jean Henri Bertin, Neuilly-sur-Seine, France, assignor to Bertin & Cie, Plaisir, France, a company of France Continuation-impart of application Ser. No. 498,314, Oct. 20, 1965, which is a division of application Ser. No. 165,634, Jan. 11, 1962, now Patent No. 3,263,764. This application June 19, 1967, Ser. No. 646,964 Claims priority, application France, Jan. 17, 1961, 849,877; June 30, 1961, 866,604 Int. Cl. B60v 1/04 US. Cl. 180-121 4 Claims ABSTRACT OF THE DISCLOSURE A ground effect machine operating on pressure fluid cushions formed against a bearing surface and defined by a plurality of skirts which are so designed, sized and arranged in relation to the rest of the machine and to the bearing surface, as to bound, in operation, substantially difierent fluid cushion volumes.

This is a continuation-in-part of my copending application Ser. No. 498,314 filed Oct. 20, 1965 and since abandoned, which is itself a divisional application of my application Ser. No. 165,634 filed Ian. 11, 1962, now Patent No. 3,263,764.

The present invention relates in general to ground effect vehicles or like bodies movable along a bearing surface such as the ground or the sea with the formation of pressure fluid cushions against said surface, and it relates more specifically to such machines of the multicushion, plenum chamber type, wherein each cushion is laterally defined by a skirt which may be rigid but is preferably flexible in order to be able to negotiate obstacles without undue damage.

Every skirt has, in operation, a natural frequency which depends basically on its design, size and arrangement with respect to the vehicle and the ground or other bearing surface and which may set up unpleasant and even harmful resonant vibrations. If, as in conventional multi-skirt ground effect machines, all the skirts are alike and have the same natural frequency, the above resonant phenomenon will only take place with amplified detrimental effects.

The main object of the present invention is to overcome this drawback and to devise a multi-skirt ground efiect machine which will perform as an aperiodic system.

This object is achieved by giving different cushion volumes to distinct plenum chambers, e.g. diiferent skirt lengths, diameters and/or leakage gap widths.

Other objects and advantages of the present invention will appear in the following description with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic elevation view, partly in section of a ground effect vehicle.

FIGURE 2 is a corresponding front elevation view.

FIGURE 3 shows in elevation, in simplified form, an embodiment of the present invention.

FIGURES 4 and 5 are similar views of two other embodiments.

FIGURE 6 shows in section alternative forms of plenum chambers.

FIGURE 7 is an underside view of still another embodiment.

FIGURE 8 is a section taken along line VIII-VIH of FIGURE 7.

Referring now to FIGURES 1 and 2, there is shown thereon a platform 1 with four gaseous cushions, each supplied by three ejectors 3, the inductive nozzles 4 of which branch 01f the discharge duct of a compressed gas generator '5, for instance a gas-turbine engine.

Each of said gaseous cushions is of the plenum chamber type and confined within a skirt 2 made of supple material and mounted on a supporting frame 7 gimballed by means of two horizontally opposed pivots 8 and supported by two horizontally opposed pivots 10 solid with the platform 1 and set at right angles to the axis of the pivots 8. The pivots 10 are preferably fixed to the walls of a flotation tank 21 disposed inside each cushion.

The upper portion of each skirt 2 provides an oscillation joint, an example being bellows joint 11, whereby the skirt is able to move freely in all directions and full tightness with minimum friction is ensured.

A control system shown diagrammatically in the form of a lever 12 controls the pivotal motion of the skirts about the two perpendicular axes containing respectively the pivots 8 and the pivots 10.

The platform is further equipped with a front orientable wheel 13 and a rear wheel 14 driven by an engine 17, for providing positive (friction) guidance and propulsion in a manner Well known in the motorcycle art. The wheels are linked to the platform 1 by arms 15, 16 provided with suspension elements 18 and 19 designed to support only 10 to 20% of the total Weight of the vehicle, the major part of the weight being supported by the gaseous cushions. The suspension elements may be adapted to permit stiffness adjustment, as shown for instance in Brueder 2,757,376.

Valves 20 enable the compressed gas supplied by the gas generating engine 5 to be distributed as desired to the various cushions.

After the engine 5 has been started up, the platform 1 rises on its" air cushions and may be piloted by movement of the control lever 12 which orientates the skirts 2. Accelerations obtained thereby, however, must be kept to a low value in order to avoid diminishing the lifting efliciency, and such acceleration will therefore be suited to translational motion and to low speed manoeuvering.

As a part of the weight of the vehicle is supported by the wheels 13, 14, the propulsion of said vehicle may be effected by means of the rear wheel and the accelerations and decelerations exceed those attained by aerodynamic means, with yet a good propulsive efiiciency. The tandem wheels will in fact ensure good stability when travelling on the ground, even at cruising speeds, if they support 10 to 20% of the weight and if the front wheel 13 is steerable as said hereinbefore. The Wheels may be fitted with tires having treads adapted to ensure good traction with the ground.

The effects of the sideway forces due to the wind are thus reduced, and the corresponding tipping couple may be further counterbalanced by suitably operating the valves 20 in a differential manner.

The skirts 2 made of flaccid (flexible though substantially nonelastic) fluidtight material, are shown in FIG- URES 1 and 2 to be cylindrical. In practice, it is preferred to use frusto-conical skirts slightly converging toward their free open end and the embodiments illustrated in the following figures will show such frustoconical skirts.

In accordance with the present invention, an improvement which is applicable to platform with multiple skirts consists in imparting different elasticity characteristics to the individual skirts supporting such platforms. As will be readily understood, the geometrical size of each skirt, namely its height and diameter, and its volume in particular, together with its stiffness and the dimensions of its associated supply duct, all affect the instantaneous rate of leakage and determine a natural period of vertical oscillations of the corresponding air cushion. If all the skirts were identical, such vertical oscillations might give rise to resonant phenomena which may detrimentally affect overall platform sustention. On the other hand, if the individual skirts be given different geometrical characteristics, as shown in FIGURES 3, 4 and 5, then the natural oscillation periods of the various air cushions will be different and the whole system will tend to be aperiodic.

Taking FIGURE 3 first, it is seen that platform 1 is fitted with two sorts of skirts: relatively long skirts 2a of relatively. large base diameter and relatively short skirts 2b of relatively small base diameter. However the arrangement is such that the mean leakage gap width as measured between the ground or sea surface and the base of the skirts, is practically the same for every skirt.

Alternatively, FIGURE 4 shows a kind of reverse arrangement with skirts of similar size and design, some of the skirts however, 20, having a smallerleakage gap than others, 2d. The fluid cushion being bounded endwise by the top end closure of the skirts and by the ground or sea surface, it is clear that in this arrangement there are differentcushion volumes for distinct skirts.

Of course, aperiodicity by cushion volume differences may be obtained by cumulating all the above geometric variations. Thus, FIGURE 5 shows the use of skirts 2e which, compared with other skirts 2 are longer, of larger base diameter and of narrower leakage gap.

Variation in cushion volume can be obtained in still other ways as for example by reducing or increasing the effective cushion volume: in FIGURE 6, part of the inner volume bounded by a skirt 2g is occupied by a filler 21 allowing the air supply discharged by a ducted fan 22 to flow into the plenum chamber, while the inner volume bounded by another skirt 2k is supplemented by that of an auxiliary enclosure 23 communicating therewith without affecting, here again, the supply flow from ducted fan 24.

Individaul or elemental skirts such as described above are preferably provided in large number and clustered together to increase platform stability, but this in turn implies a large total efllux or leakage perimeter. Therefor, when it is desired to achieve high lift efliciency, an encompassing peripheral skirt may be used in conjunction with the clustered elemental skirts. Referring now to FIGURES 7 and 8, there is illustrated thereon a peripheral skirt 41 which is frusto-conical to some degree in side elevation and has a circular dual-lobe platform. Such a skirt may be supplied separately, at an adjustable pressure, rather than be only fed with the leakages from the inner elemental skirts 2.

Adjustment of the relative heights of the skirts 2 and 41 allows selecting for the platform 1 either a high degree of stability (when the skirts 2 are relatively long with reference to the skirt 41), or great lifting efliciency (when the skirt 41 is relatively long with reference to the skirts 2).

In any case, the cushion bounded inwardly by the elemental skirts 2 and outwardly by the peripheral skirt 41 will have geometric features (length, area, volume, leak age gap) which all differ from those of the inner elemental cushions, so that a substantial aperiodicity is thereby reached.

What I claim is:

1. In a cushion confining system for a rnulti-cushion ground effect machine movable along a bearing surface and comprising supply means for feeding the cushions with pressure fluid, a plurality of closed contour walls each made of continuous fluidtight material and extending a substantial constant distance toward said bearing surface to end with a free lip adjacent to but at a small distance from said bearing surface, and a closure device to which each wall is connected at an end thereof opposite to said free lip, said walls, said closure device and said bearing surface mutually cooperating to bound definite substantially constant geometric plenum chamber volumes in which said pressure fluid cushions build up, each plenum chamber extending between a closed end level remote from said bearing surface and an open end level adjacent said bearing surface, the improvement of the distance from said bearing surface of at least one of said end levels of one plenum chamber being different from that of the corresponding end level of another plenum chamber, and the substantially constant volume of said one plenum chamber being different from that of said another plenum chamber.

2. Cushion confining system as claimed in claim 1, wherein each wall has an extension length between its end levels different from that of another wall.

3. Cushion confining system as claimed in claim 1, wherein said wall free end lips extend substantially in different planes generally parallel to said bearing surface.

4. Cushion confining system as claimed in claim 1, wherein the closure device to which one closed-contour Wall is connected is at a general level with respect to said bearing surface, which is different from that of the closure device to which another closed-contour wall is connected.

References Cited UNITED STATES PATENTS 3,332,508 7/1967 Bertin et al -121 3,371,738 3/1968 Bertin 180-121 X A. HARRY LEVY, Primary Examiner 

